The use of indicia bearing sleeves placed over the ends of electrical wire or cable for identification purposes is long known in the art. Sleeves of this type may be of the heat shrinkable or non-heat shrinkable variety depending on the various needs of the end user. Heat shrinkable sleeves are made from a material that when subjected to heat will shrink around the wire or cable and bond thereto. Non-heat shrinkable sleeves are slipped over the wire and may include an adhesive inner coating to adhere the sleeve to the wire. The sleeves may be either preprinted, that is have indicia or color coding printed thereon by the manufacturer or may be blank wherein the end user prints the desired indicia thereon. The latter has more versatility to the end user in that any desired indicia may be placed on the sleeve at an on-site location.
Wire marker sleeves of the prior art are usually formed by one of two practices. The first includes forming the wire marker sleeve from a continuous length of extruded plastic tubing which then may be cut to the desired sleeve length. Again, these plastic tubular sleeves may be supplied to the user either preprinted or without printing. When supplied without printing, the sleeves are usually flattened to permit the user to print alpha-numeric indicia thereon. However, to provide printing capability, the flattened sleeves must be supported on a fixture or other device to facilitate movement through a printing device. In U.S. Pat. No. 3,894,731, issued July 15, 1975, flattened tubular sleeves are shown carried on a support carrier consisting of a plurality of pendent tines extending from a support spline. An assembly of this type however requires modified or special printing equipment not usually available to the end user.
A second technique is known for manufacturing wire marker sleeves which is compatible with office machinery such as a typewriter or a computer printer. This technique consists of placing two sheets of plastic film in side-by-side orientation forming a two-ply marker sheet. The two sheets are sealed together with spaced longitudinal seals to provide a three dimensional strucutre of elongate sleeves which the user can feed into a typewriter or computer printer. The printed sheets can be cut into individual wire markers for use over electrical wire. A wire marker system of this type requires extensive end user preparation in order to provide individual wire marker sleeves. The end user is responsible for spacing the indicia and cutting the elongate sleeves into individual wire markers. Further, the manufacture of wire marker sheets of this type is more complex as two sheets of material must be aligned and sealed along plural longitudinal lines in order to form the various wire markers.
An improvement in the latter technique for forming wire markers is shown in U.S. Pat. No. 4,361,230 issued Nov. 30, 1982. An assembly of wire marker sleeves is formed by joining one or more top webs to a base web of material along transverse seams. The top webs have a width which is narrower than the base web. The base web also includes a series of horizontal and vertical perforations to assist in detaching the individual wire markers from the assembly. While overcoming some of the disadvantages of the previous mentioned marker sheet, the assembly shown in the '230 patent still requires the joining of one or more top layers to a base layer to provide plural wire markers. One of the inherent disadvantages resulting from the formation of wire markers from one or more flat plies of material is that upon use of the individual marker sleeve, there is great difficulty in inserting the electrical wire in the end of the sleeve as the end tends to be closed due to the flat formation of the two-ply sheet. U.S. Pat. No. 4,442,939 issued Apr. 17, 1984, shows a sheet of wire markers formed from two plies of material wherein the region between adjacent wire markers includes an aperture through one sheet. Upon severence into individual wire markers, the portion of the aperture adjacent the end of the wire marker facilitates insertion of the wire into the sleeve. However placement of the apertures in one layer of the two-ply structure requires an additional step in manufacture which could increase the cost of assembly. Further, the user must search for the precise location of the aperture upon insertion of the wire in order to facilitate ease of insertion.